Origin and the Silurian odyssey of the Brunovistulian terrane: paleomagnetic evidence from the Brno Massif (central Europe).

The Brno Massif forms a part of larger tectonostratigraphic unit named the Brunovistulian Terrane (BVT) that is one of crustal block of Europe with the Neoproterozic basement.  However, the Neoproterozoic orogenic belt was developed in wide area i.e. along the Gondwana margin and near the present day eastern and southern edge of the East European Craton. For more than 20 years, the problem of primary setting of the BVT inside the Neoproterozic orogenic  belt have been discussed. Also the path of their drift and  time of their final accretion have been a matter of debate. To solve these problems the paleomagnetic and isotope studies of vertical intrusions cutting the BVT basement near Brno in Moravia have been undertaken. Preliminary isotope dating of granitic and basaltic intrusions points to the early Silurian age of them. Results of demagnetization of paleomagnetic samples from three localities revealed the presence of stable components with a steep inclination, at that time characteristic for the northern margin of Gondawana but not for the Baltica paleocontinent that during the Silurian was situated between the equator and 30^oS. The Emsian  “old red” type deposits may indicate that final amalgamation of the BVT took place some-time between the Silurian and the Devonian. This time of joining of the BVT  to Baltica and quite high (50 – 60^oS) paleolatitudes obtained from the early Silurian rocks of the Brno Massif  point to a rapid drift of the BVT across the Rheic Ocean during the Silurian.